X-37B Might Not be Spying on China’s Space Station

So remember the Internet hubbub last week when the BBC reported that the Air Force’s X-37B space plane may well be spying on China’s new space station, Tiangong-1, since their orbits are very close? Well, it turns out that the source behind that story, Spaceflight, the magazine of the respected British Interplanetary Society ignored one key fact; the X-37B and the Chinese space station whip past each other at insanely fast speeds when their orbits intersect, points out James Oberg, a former member of the organization that came up with the claim over at Tech Talk.

The American plane’s orbit is at a steep angle with respect to that of the Chinese space station. When the two vehicles pass, they do so at speeds of up to 8000 meters per second, making it practically impossible for one to gather intelligence on the other.

Both orbits are tilted to the equator at about the same amount, 43 degrees, and both fly about 300 kilometers high. But that is as far as the resemblance goes. According to aBBC account of the article, to be published this weekend in the 55-year-old journal Spaceflight, the author and all the editorial reviewers forgot one additional parameter that you need to specify relationships between orbits. This is the point on the equator where the orbit begins its pass over the northern hemisphere: in technical terms, the RAAN.

That information is readily available for the X-37B and Tiangong-1, and it show the two satellites are orbiting in nearly perpendicular planes. The difference in RAAN is about 95 degrees, and combined with their orbital inclinations, spherical trigonometry shows the two planes are tilted 60 degrees apart.

As others have noted, the X-37Bs orbit places it in a good position to spy on the Middle East. The image above shows the X-37Bs orbit in yellow and Tiangong-1’s orbit in red. Image via Tech Talk.